A developmental and epileptic encephalopathy characterized by onset in the first weeks or months of life of refractory seizures, profoundly impaired intellectual development, absent speech, spastic quadriplegia, and dyskinetic movements that has material basis in homozygous or compound heterozygous mutation in the PIGP gene on chromosome 21q22. The disease is MONDO_0033364 (developmental and epileptic encephalopathy, 55). Also known as: DEE55, EIEE55, developmental and epileptic encephalopathy 55, epileptic encephalopathy, early infantile, 55.